1. Field of the Invention
The present invention relates to a memory system having a host and an electronic circuit card that can be inserted into the host and electrically connected to the host, and more particularly to a system and method for controlling a transmission speed between the host and electronic circuit card.
2. Discussion of Related Art
Small cards containing non-volatile semiconductor memories have become popular for storing multiple megabytes of data from personal computers, notebook computers, personal digital assistants (PDAs), smart telephones, cameras, digital recorders, MP3 players, and other electronic devices. Memory cards may be used to store video data or other data needing high capacity. The number of applications for such memory cards is increasing rapidly. An example of an application is storing music downloaded from the Internet.
MultiMediaCard (MMC) is a kind of memory card having a plurality of electrical contacts (input/output terminals). MMC is available with different storage capacities, e.g., 64 megabytes. The physical and electrical specifications for MMC memories are given in “The MultiMediaCard System Specification” (“MMCA”). Version 3.3 of the MMCA specification, dated March, 2003, is incorporated herein by reference.
MMC memory has a serial interface that uses six electrical contacts, one for transfer of data, one for receiving commands and sending responses, one to receive a clock signal and three to receive power. The rate at which data can be transferred into and out of the card is limited for a given clock frequency by use of a single data contact, as opposed to transferring data in parallel through multiple contacts as done in other larger memory cards having different formats.
The data transmission speed of MMC memory is about 1 MB/sec to 2 MB/sec. However, a high speed MMC can have a data transmission speed of about 52 MB/sec.
Therefore, a need exists for a system and method for controlling a transmission speed between a host and a memory card.